Method of cooling an accessory gearbox

ABSTRACT

The accessory gearbox (AGB) has at least one coolant passage between the AGB and the accessory for externally cooling the accessory without coolant flow inside the accessory.

CROSS-RELATION APPLICATION The present application is a divisional of U.S. patent application Ser. No. 10/886,603 filed Jul. 9, 2004, the contents of which are hereby incorporated by reference. TECHNICAL FIELD

The technical field relates generally to cooling arrangements and methods of cooling, more particularly the cooling an accessory used in an accessory gearbox of a gas turbine engine.

BACKGROUND

Gas turbine engines are often equipped with various mechanically-driven accessories which are connected to a casing referred to an accessory gearbox (AGB).

Some accessories are generating intense heat during their operation and for this reason, they require cooling. Oil in the AGB is often used for cooling the accessories, such as the starter/generator unit. Oil passages are provided inside the starter/generator unit and heat is exchanged between the oil and the internal parts of the starter/generator unit. This arrangement has been used in the past in an extensive number of designs. However, it requires oil connectors between the AGB and the electrical device, and also internal oil passages in the electrical device.

SUMMARY

In one aspect, there is provided a method of cooling a gas turbine accessory comprising the steps of: circulating engine oil from an engine oil circuit around an external side surface of the accessory, and circulating the oil within the engine to provide at least one of cooling and lubrication to at least one other part of the engine.

Still other aspects and features will be better understood with reference to the following description and the appended figures.

DESCRIPTION OF THE FIGURES

FIG. 1 schematically shows a generic gas turbine engine to illustrate an example of a general environment in which is located an accessory gearbox.

FIG. 2 is a schematic cross-sectional view of an example of an accessory located in a housing of an accessory gearbox incorporating the new arrangement.

FIG. 3 is a view similar to FIG. 2, showing a variant of the new arrangement.

FIG. 4 is a view similar to FIGS. 2 and 3, showing another variant of the new arrangement.

FIG. 5 is a block diagram illustrating an example of a coiling oil path of a gas turbine engine.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of a gas turbine engine 10 of a type provided for use in subsonic flight, generally comprising in serial flow communication a fan 12 through which ambient air is propelled, a multistage compressor 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases.

FIG. 2 schematically illustrates an accessory or other gas turbine-mounted device 20, such as a starter, generator or starter-generator unit, which is secured into an accessory gearbox (AGB) 30. The accessory 20 is partially embedded within a housing 32 of the AGB 30, thus having a significant amount, such as more than half, of its volume within the housing 32. The housing 32 of the AGB 30 is generally internally defined by an internal wall surface 34. This internal wall surface 34 can be shaped and configured to sealingly receive the external side surface 22 of the accessory 20.

An annular oil passage 36 is provided between the internal wall surface 34 of the AGB 30 and the external side wall surface 22 of the accessory 20. The example illustrated in FIG. 2 shows the passage 36 being located in the internal wall surface 34 of the AGB 30. As shown in FIG. 3, passage 36 can also be defined in the external side surface 22 of the accessory 20, or passage 36 can also be defined by recesses in a combination of both surface 34 surface 22, as shown in FIG. 4, or simply by any internal space defined within the AGB and that may be immediately adjacent surface 34. Opposite o-ring seals 40 are provided at both ends to ensure sealing.

As can be appreciated, the arrangement described herein creates a cooling jacket around the accessory 20 and allows heat to be exchanged, which may negate the need for additional cooling means, such as internal oil passages inside the accessory 20.

Oil is provided by the gas turbine's oil system (not depicted in this figure) to the annular oil passage 36 from at least one inlet oil passage 42, such as one located in the internal wall surface 34 of the AGB 30. Similarly, oil exits the annular oil passage 36 through at least one outlet oil passage 44 located in the internal wall surface 34 of the AGB 30, for return to the oil system. These inlet and outlet oil passages 42,44 may be configured and disposed to generate a constant flow of oil in the various regions of the annular oil passage 36. The flow is sufficient to provide the desired cooling to accessory 20.

FIG. 5 schematically illustrates an overall example of an oil circuit of a gas turbine engine 10. Oil is pumped from a tank 50 and sent to a filter unit 52. A heat exchanger 54 cools the oil. At least some of the oil is then provided to the accessory 20 for cooling thereof. The oil then circulates to the bearing cavities of the engine 10, for instance in the various bearings therein. Oil is then supplied to the AGB 30 before being returned to the tank 50.

The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made without departing from the scope of what is disclosed. For example, the improvements are not limited to a single annular oil passage 36. Two or more oil passages can be used and may communicate in parallel or serially with the source. The shape of the annular oil passage 36 may be any desirable and is not necessarily with a purely circular path but can include spiral-shaped paths and/or other cooling-enhancing features such as trip strips, etc. Although oil is often the coolant with which the system can be used, any suitable cooling liquid may be used. Still other modifications will be apparent to those skilled in the art, in light of a review of the present disclosure, and such modifications are intended to fall within the scope of the appended claims. 

What is claimed is:
 1. A method of cooling a gas turbine accessory comprising the steps of: circulating a coolant liquid from an engine coolant circuit around an external side surface of the accessory, and circulating the coolant liquid within the engine to provide at least one of cooling and lubrication to at least one other part of the engine.
 2. The method as defined in claim 1, wherein the step of circulating coolant liquid around the accessory includes the step of circulating coolant liquid between an inlet of a coolant liquid passage and an outlet of the coolant liquid passage to exchange heat between the coolant liquid and the external side surface of the accessory.
 3. The method as defined in claim 2, wherein the accessory is at least partially inserted in an accessory gearbox (AGB).
 4. The method as defined in claim 3, wherein the accessory has a circular cross section.
 5. The method as defined in claim 3, wherein the coolant liquid passage is at least partially axially delimited by a pair of spaced-apart seals provided between an internal wall surface of the AGB and the external side surface of the accessory, the external side surface being radially inward of the internal wall surface.
 6. The method as defined in claim 3, wherein an internal wall surface of the AGB and the external side surface of the accessory define the coolant liquid passage.
 7. The method as defined in claim 3, wherein the coolant liquid directly contacts the external side surface of the accessory to thereby cool the accessory.
 8. The method as defined in claim 7, wherein the accessory is substantially enveloped by the internal wall surface of the AGB.
 9. The method as defined in claim 7, wherein the accessory is sealingly received by the internal wall surface of the AGB.
 10. The method as defined in claim 1, wherein the coolant liquid comprises oil and the coolant liquid circuit includes a main oil circuit communicating with at least one main bearing cavity in the engine. 